Friday, December 7, 2007

3.3.1 Who's being lazy?

Amblyopia is commonly known as the lazy eye. Except for congenital opacities, a lazy eye is absolutely normal in structure, both inside and out, yet its vision is poor. The other eye, on the other hand, has good vision. To a child, the visual world would appear normal. And to others, nothing unusual about this child's eyes, either. For this reason, the discovery of amblyopia is almost all by accident, first noticed by an observant parent or a pediatrician.

There are three types of amblyopia:

Deprivational: this happens when there are cataracts or corneal opacities blocking the path of light into the eye. Naturally the opacities must be removed first.

Refractive: this type occurs due to a large difference between the refractive errors of the two eyes. For example, if one eye is normal or near-sighted and the other is very far-sighted, then the latter will remain unused to avoid diplopia - this then results in amblyopia. There is a subtype due to high astigmatism. It usually involves both eyes. And because part of the retina is never used fully, that part will become amblyopic and the vision will not achieve 20/20 even with the best correction.

Strabismic: In this type, the eye positions are not aligned or coordinated, so the less dominating eye becomes disused or suppressed on order of the brain. This eye then becomes amblyopic.

A “lazy” eye therefore is not an eye that does not want to contribute but rather it is prevented from doing so.

The treatment of amblyopia is really to force the amblyopic eye to see, by means of patching of the good eye, or by using atropine eyedrops to reduce the usage of the good eye. The earlier the treatment starts, the better the outcome.

The major problem with patching is the children’s resistance often from discomfort or teasing from their peers. Compliance using the atropine drops (once a day) is certainly easier and in fact the results are as good as that with eye patching. This was supported by a recent clinical study comparing these two methods: The improvement was 3.7 lines (on the visual acuity chart) in the patching group and 3.6 lines in the atropine group. And about half of each group can achieve a visual acuity of 20/25 or better.

So these are the two choices, both equally effective. Amblyopia in fact should not remain untreated. Unfortunately, we still see these cases from time to time.